Many medical instruments are reusable and require sterilization between uses. Some of these instruments, for example, endoscopes and gastroscopes, are difficult to fully sterilize. Typically, such instruments are sterilized by hydrogen peroxide which is flushed through the interior as well as over the exterior of the instruments. This is not only a time consuming process, taking about one hour, but often the instruments have contaminated areas which the sterilizing process cannot sufficiently penetrate to fully sterilize such as biofilms of bacteria. In addition, the hydrogen peroxide is not able to kill all viruses. Another common sterilization agent is ethylene oxide which produces similar results. Other methods of sterilization include irradiation with gamma radiation, but this method can take up to 24 hours with current equipment.